Page 88 - Moving the Earth_ The Workbook of Excavation

SURVEYS AND MEASUREMENTS

2.38 THE WORK

FIGURE 2.34A Cubitape. (Courtesy of Cubic Industrial FIGURE 2.34B Electrotape. (Courtesy of Cubic Industrial
Corp.) Corp.)

FIGURE 2.35 Corrections for curve of earth’s surface.

This level is used by holding it to one eye, and tipping it up or down until the bubble is cen-
tered at the centerline on the glass. Any object cut by this line is then on a level with the
observer’s eye, and nearby elevations may be determined and levels run in the same manner as
with an instrument.
Results are much less accurate, but in rough work this may be more than compensated by the
ease of use.
The eye height of the observer may be used as a unit of measurement. In taking the height of
a hill, as in Fig. 2.36B, the observer holds the level to her or his eye, while the rod operator moves
up or down the hill in response to instructions, until the bottom of the rod, a stick, or the operator’s